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Chasing an Hot/Overheating Issue

6K views 38 replies 11 participants last post by  Laggy 
#1 ·
2001 TJ :
Hello, I know there are lots of overheating threads, but after reading most of them I have not found anything like mine. Hoping someone has a little insight for me. My TJ has been running "hotter" than normal all spring. The temp gauge use to hold at the 1 on the 210. Recently it started to creep to the right to about the middle of the zero. 124000 miles on a 4.0 6cyl.
I changed the thermostat with a OEM 195 superstant, flushed the engine and heater core with distilled water, and now have a 50/50 mix of distilled water and the G-05 zerex antifreeze. The lower hose was soft so I did change that too.
I let it run in the driveway for almost an hour today. Sat right on the one. As soon as I cruise around town it starts to climb to the zero, and once on the interstate is crawls past the zero, and then overheats. I would think that more air coming across the radiator would cool the motor. Mine does the opposite. The faster I go the hotter it gets. It cools down sitting in traffic...
 
#3 ·
Yes, system was burped.
I checked the coolant level after it cooled, and she is full and overflow is good too. I checked the weep hole on the pump and there is no leak. What else would indicate the pump is bad? I don't mind changing it, just don't want to keep throwing cash at it...
 
#9 ·
My money says that if you've got the front of your grill restricted with stuff like I do and the only time your temperature goes up is when you are on the highway a new fan is not going to fix it. Either that or my fan is busted too, but it was working fine until I put the winch and lights in front of the grill.
 
#10 ·
Doesn't sound like the fan clutch.
Even though you flushed the system, the radiator could still have blocked passages.
Is the radiator original? If so, with 124k miles, it might be time for a new radiator.
The water pump could also be on it's way out.
If you decide to go this route, consider OEM, you can get good prices at wermopar.com
 
#12 ·
I was fighting a warmer than normal condition for a bit too, as well as a boiling overflow tank issue. A new radiator cap solved the boiling tank, but it still ran warming than normal, especially at freeway speeds. 131K miles on all original components. I drained the cooling system, added a bottle of Prestone cooling system cleaner and topped the system off with distilled water. I ran the cleaner for a total of 5 running hours(30 or so start cycles). Drained, flushed about 4 times, then 50/50 mix with Mopar embitted coolant. Also changed the thermostat. Now, It runs to the left of the dot.
 
#13 ·
I messed around with it today, and I think I am going to order a OEM radiator. Its still running hot on the highway, and too hot for my liking on the street. My wife has a 97 TJ w/197000 and it runs perfect but had a new radiator two years ago. Cannot see spending the money on the 400.00 models. This one has lasted 124,000. I have only had this TJ a year, and know nothing of the history of the jeep. It does appear to have a newer water pump, so I think a radiator is next on the list. thanks
 
#18 ·
Could be anything in the system. Mine was trashed from PO. I replaced everything but heater core. EVERYTHING. Now my system kicks ass. I probably could have replaced just thermostat and water pump and been ok for a bit.

You should be able to disconnect your hose and see if water pump spins nicely. Compare to one from a local auto store. If it spins freely, they can still be super pitted and roughed up on the inside impeller, which can cause cavitation bubbles which can in turn cause issues. A water pump replacement is super easy on 4.0's.

Most of the time overheating is one part, but sometimes a bunch of well used parts can collect their respective shortcomings into an overheat situation. In that case, replacing one part usually won't fix it. That's my experience.
 
#14 ·
Before you buy a radiator try the thermostat it may not be opening all the way, just run water in it for the test. If that's not it just dump the water and try the radiator, you will have changed the thermostat already. By the way, water will transfer heat quicker than a 50/50 mix it just boils over at a lower temp.
 
#16 ·
Removed my winch cover, drove the exact same route in even hotter temps (was 95 the last time, Saturday was 96. My temp gauge never went above 210... stayed dead center of 210 regardless of how far and how fast I drove. This is compared to the 220 +/- with the cover on the winch blocking just a little bit more air. Proof that even small changes to the amount of unrestricted air flow through the radiator make a difference, in this case between 5 and 10 degrees. So the winch cover will stay off and I'm going to invert the square LED driving lights so that they hang down in front of the winch (which is already blocking some air). Hope to get the temp down to 200 by doing this.
 
#21 ·
My 97 had the same problem, and I have fixed it

First, antifreeze will raise the boiling point, but lowers the heat transfer, My Ferrari requires water wetter and NO antifreeze for this reason.

On my Jeep, I replaced the thermostat, hoses, fan clutch, water pump, radiator cap, and replaced the radiator with a new Mopar radiator. It still overheated when stopped or driving over 60 MPH and worse when the soft top was down. I could not use the AC above 80 degrees outside temperature.

I read on the Jeep Forum that owners used multi core radiators to cure their problem. 225,000 miles ago, I ordered a 3 row radiator. The temp gauge never leaves the 195 mark with the AC on, any speed, any outside temperature (I live in Florida & it's hot here) I own 9 cars & trucks, the Jeep was the only car I own that had a single row radiator.

I now have the time to sort out other problems, and with over 310,000 miles they do come up.
 
#22 ·
I am going to order the oem radiator if this water pump doesn't do the trick. I figured that if I replace the WP, that will rule out 1 more thing. It does look new, but PO may have replaced it with a cheap reman, so I will remove, inspect and replace this weekend and see where it goes...
 
#23 ·
I sure do feel your pain. I had all sorts of cooling issues last year. Started with a water pump shaft that broke when I rapped my RPMs high to pass someone in 2nd gear and just snowballed from there. After replacing everything except radiator the temp still stayed past the 0 on 210 no matter what. Highway, sitting whatever.

Replaced with cheap NAPA , a few weeks later the drain plug fell out. That was fun.

Ordered MOPAR radiator ... Not a problem since. Now it does get a little warm, needle between 1 and 0 when I am sitting running AC but it never leaves that spot not matter how long I sit.

Hope you find the root cause. Hate dealing with issues that seem to never have an end in sight.
 
#24 ·
Update:
I had a hard time with getting the pump off. 4 out of 5 bolts came out w/o issue. The fifth out broke off. I ended up prying the pump off with two flat bars. Had to tap with a hammer. I pulled the water pump off and was able to use a little PB blaster and a vice grip to remove the broken stud. The actual water pump was broken. The plastic impeller was not functioning, since the bolt was broken. The plastic around the bolt was broke off. I will get a new bolt tomorrow and clean up the block and inspect for damage to the block. The pump had scrapes and looked rough on the back. I fished the rest of the broken plastic out of the block. Hope once this is fixed it will solve the issue.
I did order a OEM radiator so I will end up putting it in as well, but if I get it put back together before it arrives I will try it with the old radiator.
 

Attachments

#26 ·
this is what mine looked like and i consider to be pretty bad (next to a new flowkooler)


Closeup of pitting which can cause issues when combined with other neglected parts
 
#30 ·
Id double check to make sure you don't have an air bubble sitting at the temp sensor. Next hook up a scan tool, set to data and watch what the temperature reading is actually at instead of going off the temperature gauge on the dash. If there is an air bubble in the system that made its way to the temp sensor, it would spike the gauge and look like its overheating.

I'd replace the water pump regardless because the factory ones aren't that great.
 
#31 ·
Update: I did order an OEM radiator, but its been 5 days and they have not shipped it, so I got bored and put my Jeep back together last night. New water pump installed.(had to buy 1 bolt, which it is ironic that the one that broke is the long one which I didn't realize, and had to make another trip to autozone) Installed w/o issue. Drove it around after burping system, and it ran between the 1 and 0 on the 210 mark at street speed. Let it sit overnight, and no loss of fluid. I checked the oil, and its fine, no water in the oil. I drove it today and it ran hot. I didn't drive it to the overheating temp. I can say that it took a lot farther drive to get it to run past the 0. I ended up buying a Bluetooth scan tool, and pulled the data on my phone. The temp crested 250 on the interstate, which on the Gauge is the 0. So I am basically back to square one, except I have the water pump issue solved. Westbury Jeep is the place I ordered the radiator, and I spoke to them today. I should have by Friday. I will get it installed this weekend and so if I have a clogged radiator I will find out then. I am hoping this will solve issue. Its starting to frustrate me, but not big hammer time yet.
One thing I did find is the PO installed a few of these aluminum blocks to realign the drive train so that it sits close to stock height when installing the lift. Seems that the engine is tilted up on an angle, and the fan hits the shroud if you install the shroud in the factory spot. He apparently drilled new holes 1 inch lower on the shroud to raise it up to clear the fan blade. I cannot see this being an issue(bottom of shroud does cover a small part of the radiator on the bottom)

One other thing which I hope is not the problem is hot exhaust gas in the water? Has anyone experienced this issue? I cannot find any signs of a cracked head or leaking head gasket. What are some of the symptoms of gasses in the coolant? I am really hoping it ends up being the radiator...
 
#33 ·
Update:
One thing I did find is the PO installed a few of these aluminum blocks to realign the drive train so that it sits close to stock height when installing the lift. Seems that the engine is tilted up on an angle, and the fan hits the shroud if you install the shroud in the factory spot. He apparently drilled new holes 1 inch lower on the shroud to raise it up to clear the fan blade. I cannot see this being an issue(bottom of shroud does cover a small part of the radiator on the bottom)
Do you have tall motor mounts? Body lift?

Also, run some kind of flush through your system. Flush old radiator somehow, while it's off your jeep. Then put a hose nozzle to both hoses of your heater core to flush that. Flush your block if you're so inclined. THEN put everything back together and flush as a system. Drain, install new radiator, fill with whatever antifreeze and be done. Slight PITA of a process, but I only recommend this as your system should get a flush and but i personally don't like my new radiators to see any of that unnecessary junk. Just an idea.
 
#32 ·
I went through all the same issues and worries. Signs of gasses / coolant mixing is white smoke out the tail pipe. Overheating shortly after traveling. How quick depends on severity. Look at oil cap. See if there is any creamy milky substance stuck on the underside. That's another good indicator. Another easy way to tell is to open the radiator when COLD start her up and see if you have bubbles comming out. The water level will rise a little due to pump circulating but if you have a head gasket leak you'll get smoky air bubbles.

I had done every thing you have gone through and finally everything was solved with a MOPAR radiator. My water pump also had to be replaced. Good luck man. Hope the radiator is the last of your worries.
 
#34 ·
Update: I finally received my Mopar radiator in the mail this afternoon. Installed it, filled with new water and fluid, and ran in the yard for awhile. Burped the system. I noticed that the fluid going into the radiator flowed in very quickly compared to the old one. Took jeep for a ride around town, and she ran at about 196-198 degrees according to scan tool and gauge. After that I went for ride on interstate. Drove about 20 miles at speeds up to 79 mph. Temp never got hotter than 207 degrees even at close to 80 mph. As soon as I got off interstate it dropped down to 198 again and stayed cool for the entire ride back. Appears that the radiator was definitely not allowing proper water flow. All I can think of is there must have been some type of stop leak from PO that I could not flush out. This problem seems to have been solved. Thanks to all who gave me some good ideas to check for. Through the Process of elimination I did find that water pump broken, so that is a good thing. Thanks again...
 
#35 ·
Update: I finally received my Mopar radiator in the mail this afternoon. Installed it, filled with new water and fluid, and ran in the yard for awhile. Burped the system. I noticed that the fluid going into the radiator flowed in very quickly compared to the old one. Appears that the (old) radiator was definitely not allowing proper water flow.
Through the Process of elimination I did find that water pump broken, so that is a good thing.
That was my guess ("Even though you flushed the system, the radiator could still have blocked passages.")
But as you said, it worked out that you checked the water pump first.
Good to hear that your cooling system is fixed.
 
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